In the art of auto racing, "drag racing" is a competitive event wherein competing autos, or cars, seek to start and travel from a starting line or gate to and across a finish line or gate on a straight race course of predetermined length, in the least elapsed time. The race courses are straight, well maintained, paved roadways that are commonly called drag strips or strips. In the United States, drag strips are straight elongate macadam-paved roadways having central racing lane portions that are one-quarter mile long, from starting lines or gates to finish lines or gates. Typically, drag strips have short starting lane portions before the starting gates and have lengthy finish lanes that follow or continue from the finish gates.
In foreign countries where metric measurements are used, the distance between the gates is likely to be slightly more or less than one-quarter miles.
There are several different classes of drag racing cars. The most popular and important class of cars are commonly referred to as "rails". Rails are four-wheel vehicles with elongate frames and are powered by internal combustion engines. There are several different subclasses of rails, each of which is characterized by particular limitations or specifications with respect to the power plants or engines that are used to drive them.
The most powerful and fastest drag racing cars of today are powered by internal combustion engines that develop several thousands of horsepower and that drive the cars through quarter-mile courses, from start (stopped) to finish (running) in close to four seconds and with attained top speeds of close to 300 miles per hour. The engines are drivingly coupled with transversely extending rear axles of the cars which axles carry driving wheels. The driving wheels are equipped with large pneumatic tires with extensive flat pavement-engaging treads. The engines and axles are drivingly coupled by drive shaft assemblies with centrifugal clutch mechanisms engaged therein and that are such that when the clutch mechanisms are engaged, direct drive is established between the engines and axles and thence to the wheels.
A serious shortcoming that exists in the above-noted direct drive between the engines and wheels of drag cars resides in the fact that the centrifugal clutches used, upon being operated to engage, at the starting gates of drag strips, rapidly fully engage or "lock-up" completely. Further, as drag racing cars commence to move and accelerate, the speed of their engines and the horsepower generated thereby increases at a rapid rate. As a result of the two above-noted factors, there is a great tendency for the increased power delivered by the engines to the wheels of the cars to cause the tires on the wheels of the cars to lose traction with the surface of the drag strips and to spin substantially freely. When traction is lost, as noted, the desired performance of the cars is materially reduced or lost. Further, when traction is lost, control of the cars is interfered with and possibly lost, with potentially disastrous results.
In an effort to eliminate or reduce the tendency for drag racing cars to lose traction with the drag strips over which they are operated, as noted above, the operators or drivers of those cars have sought to develop skilled manual operation of the clutches to cause the clutches to slip and/or have sought to skillfully slow the rate of acceleration of the engines of the cars, as by controlling the rate of delivery of fuel to them. While such efforts were effective in the past, when the factors of time, speed and power were less critical and manually controllable, they are, with but one or two minor exceptions, of little or no practical use today. Today, the rapid rates of the changes in speed and power and the notable reductions in elapsed time have reduced operator or driver control of drag race cars to little more than timely engagement of the clutches thereof, steering the cars down or along the drag strips and shutting the engines off after crossing the finish lines or gates.
In addition to the foregoing, traction between the wheels of drag cars and the drag strips over which they are operated, is often lost as a result of varying conditions of the surfaces of the drag strips caused by variations in the weather and by variations in the composition and physical nature of the paving materials that are used. Still further, the ability to maintain traction between the tires of drag cars and drag strip surfaces is materially affected by changes and/or alterations in the size, weight and firmness of the tires, differences or variations in the rubber-like compounds of which the tires are made and certain other physical variables that are encountered and must be dealt with.
In the recent past, there are those in the art who have made efforts to provide means to manually or otherwise control and slow the rate at which the centrifugal clutches in drag race cars engage and/or to cause those clutches to slip in some controlled manner. Those mans of which we are aware have consisted of special control devices that are operatively related to the clutch release forks for the clutch mechanisms and that control operation of those forks in a predetermined manner whereby the clutches are caused to slip. To the best our knowledge and belief, those special prior art devices have attained limited and/or questionable beneficial results. This is primarily due to the fact that the release fork mechanisms of clutches are rather loose and sloppy mechanisms that cannot be satisfactorily adjusted; and, they are structurally so weak and are so poorly balanced that they cannot be made to operate accurately and dependably to cause prolonged uniform slippage of their rebuilt clutches. They are only effective to cause brief momentary slippage or total disengagement of the clutch in what might fairly be called emergency situations.